Synthesis and applications of some new nitrogen-containing heterocyclic azo-disperse dyes bearing quinoline chromophore

Article abstract of DOI:10.1007/s13738-021-02294-w

A set of five novel nitrogen-containing heterocyclic azo-disperse dyes 8 (a–d) and 10 were synthesized by diazotization of 4-bisaminoquinolines 3, followed by coupling either with rhodanine analogues 6 modified at C-5 position or α-naphthol 9. The chemica

Full text of DOI:10.1007/s13738-021-02294-w

Journal of the Iranian Chemical Society
https://doi.org/10.1007/s13738-021-02294-w
ORIGINAL PAPER
Synthesis and applications of some new nitrogen‑containing
heterocyclic azo‑disperse dyes bearing quinoline chromophore
Khalid Mahmoud Hassan1,2 · Shaban Abdel Sattar ElKhabiery 3 · Ghada Mahmoud ElHaddad 4
Sameha Hassan Shokair4 · Ibrahim ElTantawy ElSayed 4
·
Received: 17 December 2020 / Accepted: 25 May 2021
© Iranian Chemical Society 2021
Abstract
A set of fve novel nitrogen-containing heterocyclic azo-disperse dyes 8 (a–d) and 10 were synthesized by diazotization of
4-bisaminoquinolines 3, followed by coupling either with rhodanine analogues 6 modifed at C-5 position or α-naphthol 9.
The chemical structures of 8(a–d) and 10 were proven by the FT-IR, NMR, and mass spectroscopic techniques. Moreover,
utilization of these azo dyes in preparing pastes for printing polyester fabric by silk screen traditional printing was achieved.
The color strength and fastness properties of the synthesized dyes were also examined and showed moderate-to-excellent
resistance to washing, rubbing, and perspiration, as well as fastness to sublimation and light. In addition, the targeted printed
samples were screened for their in vitro antibacterial activity against both Gram-positive and Gram-negative bacterial spe-
cies. The azo compound 8a showed the best antibacterial activity against S. aureus with inhibition zone of 23 mm which is
higher than the reference drug Ampicillin (21 mm).
Keywords Amino quinolines · Azo-disperse dyes · Diazotization · Printing polyester · Antibacterial activity
Introduction
heterocyclic azo-disperse dyes compounds containing
nitrogen atom was vital structural units in dyeing textiles
and in medicinal chemistry. These derivatives proved to
be important scafolds in both textile printing and bio-
logical chemistry [5]. They had signifcant biological
activity as anticancer [6, 7], antifungal [8], antibacterial
[1, 2], antioxidant [2], antitumor [8], anti-infammatory
[9] antimalarial [8] and other industrial applications in
pharmaceutical [10, 11], cosmetic [12], photography [13],
paints [13, 14], and textiles [15]. Most dyes are classifed
according to their chemical structures [16] or application
methods. Chemical classifcation of these dyes is very
important as it depends upon the functional groups present
in a molecule [17]. Because of the wide applications of
azo compounds, it was interesting to study the synthesis of
new azo compounds, which derived from amino quinoline
motif. In addition, quinoline- and rhodanine-containing
azo dyes have numerous properties encompassing inherent
color deepening efect as a key feature of the quinoline and
rhodanine rings [18–22]. Based on the above-mentioned
facts, we aim to construct azo-disperse dyes derived from
quinoline and/or rhodanine and study their biological and
industrial applications as antibacterial and dyes on textile
fbers, respectively.
Azo-disperse dyes are one of the most common and ef-
cient classes of synthetic industrial dyes. Synthetic azo
compounds [1, 2] now became widely spread in han-
dling much applications in both medical feld and tex-
tile industries [3, 4]. In recent years, the development of
* Khalid Mahmoud Hassan
drkhalidhassan73@gmail.com;
drkhalidhassan73@el-eng.menofa.edu.eg
* Ibrahim ElTantawy ElSayed
ibrahimtantawy@yahoo.co.uk
1
Electrochemistry Research Laboratory, Physics
and Mathematics Engineering Department, Faculty
of Electronic Engineering, Menoufa University,
Menouf 23952, Egypt
2
Applied Sciences Department, Higher College
of Technology, University of Technology and Applied
Sciences, Al-Khuwair, PO Box 74, 133 Muscat, Oman
3
Dyeing, Printing and Textile Auxiliaries Department, Textile
Research Division, National Research Centre, 33 El Bohouth
street, Dokki, P.O.12622, Giza, Egypt
4
Chemistry Department, Faculty of Science, Menoufa
University, Shebin El-Kom, Egypt
Vol.:(0123456789)
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Journal of the Iranian Chemical Society
General synthetic method for rhodanine derivatives
[6]
Experimental section
Instruments and methods
A mixture of salicylaldehyde 4 (0.42 mL, 4 mmol) and
rhodanine 5a (0.95 g, 4.0 mmol) or allyl rhodanine 5b
(0.69 g, 4.0 mmol) was dissolved in Gal. AcOH acid in
presence of AcONa (0.33 g, 12.0 mmol) and then refuxed
for 4 h. The reaction completion was monitored by TLC
using DCM and EtOH mixture (5:1) as eluent. The reac-
tion mixture was cooled to room temperature and poured
dropwise into crushed ice. The precipitated product was
fltered of, washed by deionized water, and then dried to
aford 6.
All 1H- and 13C-NMR spectra were recorded on a
JEOL ECA500 FT NMR spectrometer at 500 MHz
and 100 MHz at El-Mansoura and Zagazig University
Central Laboratory, Egypt in which dimethyl sulfoxide
(DMSO-d6) was used as solvent. Chemical shifts were
expressed in δ ppm relative to the position respec-
tive to the solvent. Fourier transform infrared (FT-IR)
spectra were recorded using Thermo Fisher Nicolet
IS10, Spectral Analyses Unit, Faculty of Science,
Mansoura University, Egypt. Electron impact ioniza-
tion mass spectra (EI-MS) were obtained on a Thermos
Scientific Trace 1310 Mass Spectrometry et al.-Azhar
University, Egypt. UV/vis absorption spectra for azo
compounds were measured by a Hunter Lab Ultra Scan
PRO spectrophotometer. The in vitro antibacterial
screening was carried out at Micro Analytical Center,
Cairo University, Egypt. Melting points (m.p) were
measured and recorded by Stuart scientific melting
point apparatus and were uncorrected. All synthetized
products were detected by thin-layer chromatography
(TLC) on kiesel gel F254 precoated plates (Merck).
Compounds 3a, 6a and 6b were prepared according to
the reported methods [23–27].
2‑(2‑Hydroxybenzylidene)‑5‑thioxodihy drothio‑
phen‑3(2H)‑one [6b] Yellowish powder; yield (0.81 g, 81%);
m.p (148–150 ºC); FT-IR (cm−1)=3228 (OH), 3050 (=CH),
2924 (-CH2-), 1680 (C=O), 1588 (C=C), 1205 (C=S). 1H-
NMR (DMSO-d6, ppm): δ=4.63 (m, 2H, CH2=CH), 5.20
(m, 2H, CH=CH2), 5.83 (m, 1H, CH = CH2), 6.95–7.73
(m, 4H, CHAr), 8.07 (s, 1H, CH=C), 10.74 (br. s, 1H, OH).
EI-MS (m/z) (C13H14NO2S2): calcd, 280; found molecular
ion peak 279 [M-1]+.
General synthetic method for azoquinoline
derivatives [8 (a–d) and 10]
A mixture of the appropriate aryl amine 3a (0.27 g,
1.0 mmol) or 3b (0.36 g, 1.0 mmol) and concentrated
(conc. HCl) acid (2.0 mL, 34%) in 25.0-mL glass beaker
was stirred using a magnetic stirrer and subsequently
cooled to 0–5 °C in an ice bath. An aqueous solution of
NaNO2 (0.069 g, 1.0 mmol) in water (3.0 mL) is then
added slowly. The produced diazonium salt 7 was stirred
for an extra 30 min at 0–5 °C. In a separate glass beaker,
cooled rhodanine analogues 6 modified at C-5 posi-
tion or α-naphthol 9 (1.0 mmol) was dissolved in EtOH
(5.0 mL) and cooled to 0–5 °C, and then, Na 2CO3 (1.0 g,
10.0 mmol) was added. The produced mixture was vig-
orously stirred in the ice bath at 0–5 °C, while the cold
diazonium salt solution was added portion-wise. After stir-
ring for an extra two hours, the crude product was fltered
of under vacuum, washed several times with distilled
water (5.0 mL), recrystallized from EtOH, and air-dried
to aford the azo compounds 8(a–d) and 10 in excellent
yields.
Chemicals and reagents
4,7-Dichloroquinoline (99%), 1,4-phenylenediamine
(99%), 4,4′-methylenedianiline (97%), rhodanine
(97%), and allyl rhodanine were obtained from Sigma
Aldrich. α-Naphthol (99%), salicylaldehyde (99%),
triethylamine (Et3N) (99%), ethanol (EtOH) (99%),
glacial acetic acid (Gal. AcOH, 99.7%), dichlo-
romethane (DCM, 99.8%), hydrochloric acid (HCl,
35.4%), sodium nitrite (NaNO2, 98%), sodium car-
bonate (Na2CO3, 98%), sodium dihydrogen phosphate
(98.0%), and sodium lignosulfonate (anionic dispers-
ing agent, powder) (99.5%) were bought from LOBA
Chemie. Sodium acetate (AcONa, 99%) was obtained
from East-Chem. Thickener (commercial synthetic
thickener) acrylate copolymers and Lyprint (sodium
salt of nitrobenzene sulfonic acid) were supplied from
BASF Company. Polyester (150 g/m2) were supplied
by Egyptian and developing Co., Cairo, Egypt. Daico
thick 1600, a synthetic thickener for azo-disperse silk
screen-printing, was supplied by Daico company. All
chemicals and reagents were used without any further
purification.
5‑((4‑((7‑Chloroquinolin‑4‑yl) amino) phenyl) diazenyl)‑2‑
hydroxybenzylidene)‑2‑thioxothiazolidin‑4‑one [8a] Yel-
low powder; yield (0.80 g, 80%); m.p (178–180 °C); FT-IR
(cm−1)=3661–3353 (OH), 3462 (NH), 3039 (=CH), 1675
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Journal of the Iranian Chemical Society
(C=O), 1568 (C=C), 1526 (CN), 1450 (N=N), 1221 (C=S).
1H-NMR (DMSO-d6): δ = 6.90- 7.95 (m, 9H, CHAr), 8.14
(s, 1H, HC=C), 8.45–8.62 (m, 3H, CHAr), 9.30 (br. s, 1H,
NH), 9.30, 9.51 (br. s, 2H, 2NH), 10.41 (s,1H, OH). 13C-
NMR (DMSO-d6): δ = 101.38, 116.11, 117.75, 119.81,
121.72, 122.86, 123.96, 124.83, 125.76, 126.94, 127.97,
128.97, 131.63, 132.05, 135.02, 137.18, 143.14, 147.69,
149.95, 151.91, 157.34, 173.31, 197.89.EI-MS (m/z)
(C25H16ClN5O2S2): calcd, 517; found molecular ion peak
517 [M+].
199.52. EI-MS (m/z) (C35H26ClN5O2S2): calcd, 648; found
molecular ion peak 648 [M+].
4‑((4‑(4‑((6‑Chloronaphthalen‑1‑yl) amino) benzyl) phenyl)
diazenyl) naphthalen‑1‑ol [10] Dark brown powder; yield
(0.71 g, 71%); m.p (130–132 °C); FT-IR (cm−1) = 3662–
3279 (OH), 3241(NH), 2923 (–CH), 1596 (C=C), 1533
1
(C=N), 1450 (N=N). H-NMR (DMSO-d6): δ = 4.16 (s,
2H, CH2), 7.00–7.90 (m, 16H, CHAr), 8.20 (m, 2H, CHAr),
8.88 (m, 1H, CHAr), 9.30 (s, 1H, NH), 11.12 (br. s, 1H, OH).
EI-MS (m/z) (C32H23ClN4O): calcd, 514; found molecular
ion peak 514 [M+].
5‑((4‑((7‑Chloroquinolin‑4‑yl)amino)phenyl)diazenyl)‑2‑h
ydroxybenzylidene)‑2‑thioxothiazolidin‑4‑one [8b] Dark
yellow powder; yield (0.78 g, 78%); m.p (140–142 °C);
FT-IR (cm−1)=3706–3118 (OH), 3419 (NH), 3058 (=CH),
2924 (-CH), 1701 (C=O), 1571 (C=C), 1527 (C=N), 1450
Textile printing
Preparation of printing paste
1
(N=N), 1209 (C=S). H-NMR (DMSO-d6,ppm): δ = 4.63
(d, J = 5.0 Hz, 2H, –CH2), 5.18 (m, 2H, HC=CH2), 5.82
(m, 1H,CH=CH2), 7.33–7.91 (m, 9H, CHAr), 8.14 (s, 1H,
CH=C), 8.34–8.45 (m, 3H, CHAr), 9.20 (br. s, 1H, NH),
10.80 (br. s, 1H, OH). EI-MS (m/z) (C28H20ClN5O2S2):
calcd, 557; found molecular ion peak 556 [M-1]+.
Each printing paste was prepared using the proportions
shown in Table 1.
The aforementioned printing paste was applied to polyes-
ter fabrics according to conventional screen-printing method
[28]. Prints fxation was carried out by drying at room tem-
perature followed by thermo-fxation for 4 min at 180 °C.
The prepared prints were rinsed in hot water, cold water and
soaped with 2.0 g/L nonionic detergent at 60 °C for 30 min,
respectively.
5‑((4‑(4‑((6‑Chloronaphthalen‑1‑yl) amino) benzyl) phenyl)
diazenyl)‑2‑hydroxybenzylidene)‑2‑thioxothiazolidin‑4‑one
[8c] Yellow powder; yield (0.83 g, 83%); m.p (170–172 °C);
FT-IR (cm−1)=3721–3147 (OH), 3411 (NH), 3030 (=CH),
2920 (CH2), 1702 (C=O), 1573 (C=C), 1512 (C=N), 1448
Determination of antibacterial activity
1
(N=N), 1212 (C=S). H-NMR (DMSO-d6): δ = 4.06 (s,
2H, CH2), 6.85–7.82 (m, 13H, CHAr), 8.14 (s, 1H, CH=C),
8.41- 8.45 (m, 3H, CHAr), 9.23 (br. s, 2H, 2NH), 10.40
(s, 1H, OH). 13C-NMR (DMSO-d6): δ = 101.36, 116.14,
117.89, 119.77, 120.86, 122.63, 123.29, 123.92, 124.96,
125.26, 127.98, 128.85, 129.78, 129.90, 131.70, 134.71,
137.39, 137.48, 137.88, 144.48, 145.20, 148.00, 149.19,
150.73, 151.93, 158.57,160.10, 162.35, 198.79. EI-MS (m/z)
(C32H22ClN5O2S2): calcd, 607; found molecular ion peak
607 [M+].
The target polyester-printed azo dyes were further used indi-
vidually to analyze its antibacterial activity against human
pathogens, Gram-positive bacteria such as Staphylococcus
aureus ATCC6538, Bacillus subtilis ATCC6633, and Strep-
tococcus faecalis and Gram-negative bacteria for instance
Escherichia coli ATCC8739, Pseudomonas aeruginosa
ATCC9022, and Neisseria gonorrhoeae.
Each bacterial strain was inoculated in to L. B. broth
media and incubated at 35 2 °C for 24 h, then, 100 µL
of each bacterial strain (1×108 CFU/mL) was seeded onto
Muller Hinton agar media under aseptic condition and
poured into petri dishes. 1.0 cm2 of polyester-printed azo
dyes were aseptically prepared and put onto the surface of
5‑((4‑(4‑((6‑Chloronaphthalen‑1‑yl) amino) benzyl) phenyl)
diazenyl)‑2‑hydroxybenzylidene)‑2‑thioxothiazolidin‑4‑one
[8d] Dark yellow powder; yield (0.65 g, 65%); m.p (136–
138 °C); FT-IR (cm−1)=3706–3118 (OH), 3388 (NH), 3031
(=CH), 2920 (CH), 1684 (C=O), 1579 (C=C), 1511 (C=N),
1453 (N=N), 1206 (C=S). 1H-NMR (DMSO-d6): δ=3.98 (s,
2H, CH2), 4.63 (s, 2H, –CH2), 5.15 (m, 2H, HC=CH2), 5.82
(m, 1H, CH=CH2), 6.85–7.88 (m, 13H, CHAr), 8.13 (s, 1H,
CH=C), 8.34 (m, 3H, CHAr), 9.20 (br. s, 1H, NH), 10.78 (s,
1H, OH). 13C-NMR (DMSO-d6):δ=46.00, 101.40, 116.11,
116.32, 117.77, 117.98, 119.22, 119.92, 120.03, 120.64,
123.29, 124.56, 124.93, 126.80, 127.95, 128.91, 129.68,
129.73, 129.83, 130.32, 131.61, 133.17, 134.34, 137.15,
137.73, 148.48, 148.85, 151.09, 151.90, 158.54, 166.79,
Table 1 The components of the printing paste
Dye
Thickener
Lyprint
4.0 g
75.0 g
3.0 g
Sodium dihydrogen phosphate
Sodium lignosulfonate
5.0 g
1.0 g
Water
Total
12.0 g
100.0 g
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Journal of the Iranian Chemical Society
seeded Muller Hinton agar plate and kept in the refrigerator
for 2 h before incubation at 35 2 °C for 24 h. After incuba-
tion, the plates were examined and the diameters of inhibi-
tion zones (mm) were recorded around the fabric samples.
The antibacterial behaviors of loaded polyester fabrics were
analyzed after four washing cycles for the following treat-
ments; (A) standard disk of ampicillin (antibacterial agent)
as positive control, (B) starting material which coded as 1
(4,7-dichloro quinoline), (C) untreated polyester fabrics as
negative control, and (D) polyester fabrics loaded with azo
dyes 8(a–d) and 10 [29].
quinoline-rhodanine or quinoline-α-naphthol conjugates
are outlined in the schemes below. The starting 4-bisami-
noquinolines 3 were obtained in good yields according to
the reaction of 4,7-dichloroquinoline 1 with equimolar ratio
of 1,4-phenylene diamine 2a or 4,4′-methylenedianiline 2b
dissolved in EtOH in presence of Et3N as a base under refux
for (14 -18 h) as shown in Scheme 1.
The plausible mechanism for the formation of 3 is
depicted in Scheme 1. The nucleophilic aromatic substi-
tution (SNAr) of the amine nitrogen to the chloride ion at
position C-4 is activated by the quinoline ring nitrogen via
negative mesomeric efect through the formation of a reso-
nance-stabilized anion A. This will assist the nucleophilic
displacement of the chloride at C-4 position by amines nitro-
gen followed by its abstraction with the aid of Et3N base
to form triethylamine hydrochloride salt (Et3N. HCl). The
new C–N bond formation via charged intermediates A and
B eventually lead to the formation of the expected 4-bisami-
noquinolines 3 as depicted in Scheme 1.
The protocol method as following, 100 µL of the tested
bacteria were grown in 10 mL of fresh media until they
reached a count of approximately 108 cells/mL for bacteria
[30, 31]. 100 µL of bacterial suspension was spread onto
the agar plates corresponding to the broth in which they
were maintained. Isolated colonies of each organism that
might be playing a pathogenic role should be selected from
primary agar plates and tested for susceptibility by disk dif-
fusion method [32]. Plates inoculated with Gram-positive
and Gram-negative bacteria were incubated at 35–37 °C
for (24–48 h) and yeast as Candida albicans incubated at
30 °C for (24–48 h). The diameters of the inhibition zones
were measured in millimeters [29]. Standard disks of Ampi-
cillin (antibacterial agent) served as positive controls for
antibacterial activity and flter disks impregnated with 10
µL of solvent (deionized water, chloroform, DMSO) were
used as a negative control. Blank paper disks (Schleicher &
Schuell, Spain) with a diameter of 8 mm were impregnated
10 µL of tested concentration of the stock solutions. When
a flter paper disk impregnated with a tested chemical is
placed on agar, the chemical will difuse from the disk into
the agar. This difusion will place the chemical in the agar
only around the disk. The solubility of the chemical and its
molecular size will determine the size of the area of chemi-
cal infltration around the disk. If an organism is placed on
the agar, it will not grow in the area around the disk if it is
susceptible to the chemical. This area of no growth around
the disk is known as a "Zone of inhibition" or " Clear zone."
For the disk difusion, the zone diameters were measured
with slipping calipers of the National Committee for Clini-
cal Laboratory Standards [30, 31]. Agar-based methods such
as Etest and disk difusion can be good alternatives because
they are simpler and faster than broth-based methods [33].
Furthermore, structure-bearing quinoline-rhodanine con-
jugates were obtained via Knoevenagel condensation reac-
tion [34, 35]of salicylaldehyde 4 with equimolar ratio of
rhodanine analogues 5 in presence of AcONa/Gal.AcOH
acid mixture as the catalyst. The reaction medium aforded
phenolic-rhodanine congers 6 in good yields as depicted in
Scheme 2.
The structure of compound 6b was elucidated by FT-IR,
1H-NMR and mass spectral analysis. The FT-IR spectra
showed a characteristic OH broadband at 3228 cm−1. While
the>C=O and>C=S groups exhibited characteristic bands
1
at 1680 and 1205 cm−1, respectively. H-NMR indicated
doublet at 4.63 ppm which corresponds to –CH2-aliphatic,
the multiplet appeared at 5.20 ppm corresponding to termi-
nal olefnic protons (CH=CH2), the multiplet appeared at
5.83 ppm relating to internal olefnic proton CH=CH2, the
singlet appeared at 8.07 ppm is related to exocyclic bond
CH = C, and broad singlet appeared at 10.74 ppm for OH
phenolic proton. The mass spectral analysis showed the
expected molecular ion peaks, which confrmed the chemi-
cal structure.
The plausible mechanism for the formation of 6 through
Knoevenagel condensation reaction was given in the follow-
ing Scheme 2. This C–C bond formation reaction involved
deprotonation of hydrogen from the active methylene group
in rhodanine ring in 5 by the aid of AcONa as a base to
aford the anionic intermediate A in situ. The subsequent
nucleophilic addition of A to the electrophilic carbon atom
of the formyl group in salicylaldehyde 4 yielded the inter-
mediate B. Further, protonation of B with AcOH ease the
dehydration with expelled of water to form the 6 in excellent
yields as depicted in Scheme 2.
Results and discussion
Chemistry
In this study, we probed the synthesis, textile printing,
and antibacterial evaluation of newly developed hetero-
cyclic azo-disperse dyes. The synthetic approaches for
Having the starting key components 3 and 6 in hand,
the formation of azo dyes 8 (a–d) and 10 was achieved in
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Journal of the Iranian Chemical Society
R1
Cl
NH2
HN
N
R1
EtOH, Et3N
Reflux (14- 18hrs)
NH2
H2N
+
Cl
N
Cl
3a, b
3a: R1= -C6H4-
b: R1= -C6H4-CH2-C6H4-
2a, b
1
NH2
R1
Cl
R1
H
Cl
HN
H2N
N
N
H
Et3N.HCl salt
Cl
N
A
Cl
- Cl
B
Scheme 1 Synthesis of 4-(bis-amino) quinolines 3
O
S
R2 N
S
H
H
S
S
O
OH
2 N
AcO Na, Reflux (3-4hrs)
AcOH
R
H
OH
+
H
H
O
O
5a, b
A
4
4
AcOH
S
H
O
S
H
S
S
R2 N
OH
R2 N
OH
H
O
O
- AcOH, - H2O
AcO Na
B
6a, b
6a: R2= -H
b: R2= -CH2-CH=CH2
Scheme 2 Synthesis of congers 6 by Knoevenagel condensation reaction
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Journal of the Iranian Chemical Society
R1
R1
N N Cl
HN
NH2
HN
N
i) Conc. HCl ii) NaNO2 . H2O
Ice cooling
Cl
Cl
N
7a, b
3a, b
3a: R1 = -C6H4
b: R1 = C6H4-CH2-C6H4-
7a: R1 = -C6H4
b: R1 = C6H4-CH2-C6H4-
Scheme 3 Synthesis of the diazonium salts 7
two-step reactions. The frst step included the diazotiza-
tion of bisaminoquinolines 3 with conc. HCl and NaNO2
solution under ice cooling to aford the corresponding
non-isolable reactive intermediate, quinoline diazonium
chloride 7 as given in Scheme 3.
The second step included the coupling of the diazonium
salt 7 (electrophile) with electron-rich component (nucleo-
phile) such as phenolic derivatives 6 and 9. This reaction
was performed via an electrophilic aromatic substitution
mechanism. The hydroxyl group directs the quinoline
R2
S
R1
N
N
N Cl
OH
HN
N
S
O
S
R1
N
S
Na2CO3
N
HN
N
+
Cl
N
Ice cooling
O
R2
OH
Cl
8 (a-d)
6a, b
7a, b
7a: R1= -C6H4-
b: R1= -C6H4-CH2-C6H4-
8a: R1= -C6H4-, R2= H
b: R1= -C6H4 , R2= -CH2-CH=CH2-
c: R1= -C6H4-CH2-C6H4-, R2= H
d: R1= -C6H4-CH2-C6H4-,
R2= -CH2-CH=CH2-
OH
Na2CO3
Ice cooling
9
R1
HN
N
N
N
Cl
OH
10
10: R1= -C6H4-CH2-C6H4-
Scheme 4 Synthesis of azoquinoline derivatives of 8(a–d) and 10
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Journal of the Iranian Chemical Society
diazonium ion to the para site of OH group in 6 and 9 under
basic condition to aford the required azo-dye compounds
8 (a–d) and 10 in excellent yields as depicted in Scheme 4.
The structure of compounds 8 (a–d) and 10 was charac-
7.88 to 8.14 ppm for (–CH=C) exocyclic double bond which
attached to rhodanine ring for 8 a–d. In addition, two broad
NH singlet appeared at 9.30 and 9.51 ppm for 8a. The azo
compounds 8 b–d showed a broad singlet at 9.20, 9.23 and
9.20 ppm, respectively, corresponding to the NH group. On
the other hand, the phenolic OH proton for 8 a–d displayed
a broad singlet ranging from 10.40 to 10.78 ppm. The 13C-
NMR (DMSO-d6) of 8 a, c and d showed signals at 166.79,
173.31, and 162.35 ppm for the carbon atom of>C=O group,
and signals at 197.89, 198.79, and 194.52 ppm for the carbon
atom of>C=S group, respectively.
1
terized by FT-IR, H, 13C-NMR and mass spectral analy-
sis. The FT-IR spectra showed characteristic NH broad-
bands at 3462, 3419, 3411, 3388 cm−1 for 8a, b, c and d,
respectively. The OH group for 8 a–d exhibited a charac-
teristic broadband ranging from 3118 to 3721 cm−1. Fur-
thermore,>C=O group for 8 a–d showed absorption band
ranging from 1701- 1684 cm−1. Moreover, the azo (–N=N–)
group for 8 a–d showed a characteristic band ranging from
1450 to 1426 cm−1. 1H-NMR indicated singlet at 4.06 and
3.98 ppm assigning to the aliphatic protons of (–CH2) for 8
c and d. Moreover, the allylic methylene proton (–CH2) of
8 b appeared at 4.63 ppm (J=5.0 Hz), while the multiplet
appeared at 5.15 and 5.18 ppm corresponding to the terminal
olefnic proton (–CH=CH2) of the allyl group in 8 d and b,
respectively. In addition, the multiplet appeared at 5.82 ppm
corresponding to the internal olefnic proton (–CH=CH2) for
both 8 b and d. Furthermore, singlet appeared ranging from
The FT-IR spectrum for 10 showed broad OH absorp-
tion band ranging from 3662 to 3279 cm−1, while exhibited
a broad absorption band at 3241 cm−1 for the NH group.
The absorption peaks appeared at 2923 and 1410 cm−1 cor-
responding to the aliphatic (–CH2) and azo groups, respec-
tively. 1H-NMR spectrum for 10 showed NH and OH broad
singlet at 9.30 ppm and 11.12 ppm, respectively. The mass
spectral analysis for all products 8 (a–d) and 10 showed the
expected molecular ion peaks which confrmed the chemi-
cal structures.
6
OH
OH
S
S
S
S
N
N
O
O
R2
R2
H
R1
N
R1
HN
N
N
Cl
N
N
HN
N
Cl
Cl
Cl
7
A
-HCl
R2
N
S
S
O
R1
N
N
HN
OH
Cl
N
8 (a-d)
Scheme 5 Suggested mechanism of azoquinoline derivatives 8 (a–d)
1 3

Journal of the Iranian Chemical Society
Scheme 6 Suggested mecha-
nism of azoquinoline derivative
10
9
OH
N
OH
H
R1
N
R1
HN
N
N
Cl
N
HN
N
Cl
Cl
Cl
7
A
-HCl
R1
N
N
HN
OH
Cl
N
10
The proposed mechanism for the azo-dye formation is given
in Schemes 5 and 6. The frst step involved the formation of
resonance-stabilized carbanion of phenol-rhodanine congers
6 and α-naphthol 9. The second step included nucleophilic
phenol-rhodanine or nucleophilic naphthol-quinoline congers
generation, then attacks the electrophilic diazonium nitrogen in
7 to form the rhodanine-quinoline or quinoline naphthalic azo
dyes 8 (a–d) and 10 as depicted in Scheme 5 and Scheme 6.
The K/S values were calculated from the refectance val-
ues at the corresponding wavelength for each dye. As esti-
mated from our experiments, the k/s for the prepared dyes; 8
a, b, c, d, and 10 was measured at their corresponding wave-
lengths; 410, 425, 415, 412, and 435 nm, respectively. The
obtained values represent the depth of dyeing which are pro-
portional to the amount of colorant present in the dyed fab-
rics [36]. Table 2 shows color strength value (16.88) of azo
compound 10 is higher than 8 (a–d), due to higher absorp-
tion of azo compound 10 (435 nm) than 8(a–d). This due to
the high conjugation of 10, the absorption peak wavelengths
shifted toward the long wavelength region and the absorp-
tion peaks were larger than other dyes 8(a–d). The lightness
(L*) of azo compound 10 (36.56) is lower than 8 (a–d). As
the lower in lightness (L*), the deeper in the color on dyed
fabric [37]. The chroma (saturation) (c*) and hue angle (h°)
are calculated by using following equations [38, 39]:
√
Color strength measurements (K/S) and analyses
Color measurements
The colorimetric strength data of the printed polyester fabric
samples were measured by light refectance technique using
a Hunter Lab Ultra Scan PRO spectrophotometer. The color
strength was expressed as (K/S value) using the following
Kubelka–Munk Eq. 1.
c ∗= (a ∗)2 + (b ∗)2
(2)
(1 − R)2
(1)
K∕S =
(
)
2R
a ∗
b ∗
h = tan−1
(3)
where R is a decimal fraction of the refection of the dyed
fabric, K is an absorption coefcient, and S is a scattering
coefcient.
The color hues of the dyes 8 (a–d) and 10 on the polyester
fabric were shifted in the reddish—yellowish direction due
1 3

Journal of the Iranian Chemical Society
Table 2 Color assessment of
the printed azo-disperse dyes
samples
Dye
Color shade
Absorption
K/S
L*
a*
b*
C*
h
[λmax (nm)]
8 a
8 b
8 c
8 d
10
Yellow
Yellow
Yellow
Yellow
Brown
410
425
415
412
435
12.14
13.66
12.88
13.79
16.88
56.14
54.18
59.44
55.14
36.56
15.14
16.12
17.58
16.12
26.15
33.14
44.61
40.88
35.68
19.22
35.32
44.78
39.23
38.14
32.78
65.18
69.88
69.14
65.99
35.81
Lightness (L*), degree of redness (+ve) and greenness (ve) (a*), degree of yellowness (+ve) and blueness
(-ve) (b*), chroma (C*), hue (h) and color strength (K/S)
to the positive values of a* and b*, respectively. Dye 10
produced higher color strength than dyes 8a–d. This is due
to the high conjugation of the naphthol coupler of dye 10
comparing with the rhodanine couplers in dyes 8a–d.
Perspiration fastness The color fastness to perspiration
(acid and alkaline) was determined according to the method
ISO 105-E04 [42]. It refers to the ability not to fade and not
to stain when the dyed fabric is perspired. It is measured
in accordance with the standard grey scale rating from 1 to
5 as (1) is poor and (5) is excellent. The polyester fabric
printed with dyes 8d showed very good-to-excellent results
(4–5) than other printed dyes 8a, b, c, and 10 which indi-
cated moderate-to-excellent results rating (2–5) (Table 3).
The higher the molecular weight of the dye, the lower rate
of dye removal according to the infuence of perspiration
solution [48].
Fastness properties
The fastness properties of the printed samples were meas-
ured to washing, perspiration, rubbing, light, and sublima-
tion according to the standard ISO methods [40–44].
Washing fastness The color fastness to washing was meas-
ured according to the method ISO 105-C06 B2S [40]. Wash
fastness is measured the resistance of dyed fbers to retain
color when they are washed by detergents and soaps. The
change in color of the dyed samples and the staining of the
adjacent fabric is detected according to the standard grey
scale as (1=poor, 2=moderate, 3=good, 4=very good,
5=excellent). The polyester fabric printed with dyes 8d and
10 showed very good-to-excellent results (4–5) than other
printed dyes 8a, b, and c which showed moderate-to-excel-
lent results rating (2–5) as shown in Table 3. This due to
the larger size of 8d, it will be entrapped inside the inter-
polymer chain space of a poly ester fber and increasing of
hydrophobic nature by increasing aromatic rings of these
dyes [45, 46]. The stability of dye 10 toward washing may
be attributed to the good penetration and afnity of the dye
10 to the fber structure which prevents the dye molecule
from transferring to the fber surface [47].
Rubbing fastness The color fastness to rubbing (wet and
dry) was detected according to method ISO 105X12 [41].
It determines the degree of color transfer from the surface
of the dyed fabric to another adjacent undyed fabric surface
by rubbing. It was measured according to the standard gray
scale which is rated between (1–5). The grade (1) is poor
and (5) is excellent. The polyester fabric printed with dye
10 indicated very good-to-excellent results (4–5) in wet and
dry fber. While the printed dyes 8(a–d) appeared moderate-
to-very good results rating (2–4) (Table 3). Also, due to the
high difusion of dye 10 molecule into the fber than other
dyes 8 (a–d) [49, 50].
Light fastness The color fastness to light was evaluated
according to method ISO 105-B02 [44]. It measures the
duration and the degree to which printed dyes resist fad-
Table 3 Fastness properties of
the polyester fabric printed with
dyes 8 (a–d) and 10
Sample
Light fastness Washing fastnessa
Rubbing
Wet
Perspiration
fastnessa
St
Alt
Dry
St
Alt
8a
8b
8c
8d
10
6
5
6
6
7
3–4
3–4
4–5
4–5
4–5
3–4
4–5
2–3
4–5
4–5
2–3
4
3–4
3–4
4–5
3–4
2–3
4–5
4
3–4
3–4
2–3
4–5
3–4
4–5
3–4
2–3
4
4–5
4–5
aAlt. is an alteration in color and St. is a staining on cotton
1 3

Journal of the Iranian Chemical Society
ing because of constant light exposure. It was determined
in accordance with the standard blue scale (1–8) as (1) is
very poor and (8) is excellent. The printed dye 10 showed
excellent result (7), while printed dyes 8(a–d) showed
good-to-very good results (5–6) as given in Table 3. The
high results of 10 and 8 (a–d) light due to the presence of
electron withdrawing group (Cl) which increase brightness
[51] in quinoline moiety of all dyes. The higher fastness to
light of printed dye 10 than 8 (–d) could be attribute to the
huge electron-donating groups in 8(a–d) which reduce the
brightness properties [51].
Antibacterial activity
The target azo-disperse dye-printed samples were tested for
their in vitro antibacterial activity against Gram-positive (,
i.e., Bacillus subtilis, Staphylococcus aureus, and Strepto-
coccus faecalis), and Gram-negative (i.e., Pseudomonas
aeruginosa, Escherichia coli, and Neisseria gonorrhoeae)
bacteria using the difusion method [53]. The azo-disperse
dye-printed samples activity increased by increasing the
size of the zone of inhibition comparing to the reference
drug Ampicillin as shown in Table 5. If the detected zone
of inhibition is greater than or equal to the size of the refer-
ence drug inhibition zone, azo-disperse dye-printed samples
are sensitive. Our investigation showed that the untreated
polyester fabrics had no antibacterial activities against
selected pathogenic bacteria. On the other hand, the starting
materials (1 and 3) exhibit low antibacterial activities with
inhibition zones ranging between 9 and 10 mm. Among all
tested samples, polyester loaded with azo dye 8 a was found
to be highly active against all the tested bacterial strains
followed by polyester loaded with 8 c. Data analysis high-
lighted that polyester fabrics treated with azo dyes 8 (a–d)
showed broad spectrum than azo dye 10 of antibacterial
activities with varied inhibition zones when compared to
reference drug Ampicillin. The azo compound 8a showed
Sublimation fastness The color fastness to sublimation was
estimated according to method ISO 105P01 [43]. It deter-
mines the ability of the printed dyes resistance toward high
temperature and pressure. It was measured using a fxom-
eter at180 and 2100C according to the standard grey scale
(1–5) which (1 = poor, 5 = excellent). The printed dye 10
indicated very good-to-excellent results (4-5) while the
printed dyes 8(a–d) showed good-to-excellent results rating
(2-5) against high temperature and staining as presented in
Table 4. The good results of sublimation fastness contrib-
uted to the polarity of the substituent groups such as pres-
ence of OH and NH groups in dyes 10 and 8 (a–d) [52].
Table 4 Sublimation fastness
Sample
Sublimation fast-
ness at 180 °C
Sublimation fast-
ness at 210 °C
Staining on fabric after
sublimation polyester
Staining on fabric
after sublimation
cotton
properties of the polyester fabric
printed with dyes 8(a–d) and 10
8 a
8 b
8 c
8 d
10
4–5
4
4
4–5
4–5
4–5
3–4
3–4
3–4
4–5
3–4
3–4
4
3–4
4–5
4
3–4
3–4
2–3
4–5
Table 5 Antibacterial activity
for polyester-printed azo-
Compounds
Diameter of inhibition zone (mm)
Gram-positive
disperse dyes against Gram-
positive and Gram-negative
bacteria after 4 washing cycles
Gram-negative
B. subtilis S. saureus S. faecalis E. coli N. gon-
orrhoeae
P. aeruginosa
Ampicillin
1
3a
3b
26
10
–
13
–
21
9
–
12
–
27
9
9
11
–
25
10
–
13
–
28
9
–
10
–
26
9
–
10
–
Untreated polyester
Polyester treated with 8a
19
13
13
12
–
23
10
16
10
–
17
11
14
12
12
18
12
14
11
–
17
11
13
12
–
15
11
13
10
–
8b
8c
8d
1 3

Journal of the Iranian Chemical Society
8. A. Aboelnaga, T.H. El-Sayed, Green Chem. Lett. Rev. 11, 254–
263 (2018)
the best antibacterial activity against S. aureus with inhibi-
tion zone of 23 mm which is higher than the reference drug
Ampicillin with inhibition zone 21 mm. Table 5 illustrates
results of the polyester fabrics dyed with synthesized dyes
after washing four times. The inhibitory efect of the newly
synthesized azo dyes could be attributed to their efcacy to
adhering to the bacterial cell wall and cytoplasmic mem-
brane and then changing in selective permeability function
which leads to the leakage of the cellular components and
hence bacterial death [54]. Also, the synthesis of new azo-
cleaved compound such as amines as a result of entering
azo dyes to bacterial cells are responsible for toxic efects
[55, 56]. Moreover, the newly synthesized compounds can
be inhibited bacterial growth through inactivation of protein
synthesis via reacting with thiol group [57], or inhibit DNA
replication through reacting with phosphorus moieties [58].
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New class of azo dyes containing quinoline chromophore
was designed, synthesized, and characterized. The synthe-
sized dyes were applied for silkscreen printing on polyes-
ter fabrics. Color measurements and fastness properties of
the prepared dyes exhibited a high efciency for washing,
perspiration, rubbing, light, and sublimation fastness. The
satisfactory performance and good antibacterial properties
of the synthesized dyes lead to design of novel antibacte-
rial disperse dyes with increasing the efcacy of application
properties.
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Acknowledgements The authors are grateful to the Electrochemistry
Research Laboratory, Faculty of Electronic Engineering, Menoufa
University, Egypt, for providing all facilities of research work.
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